I often want to make a post or album visible to the public in Google+, but I do not want to bother people by letting it show up on the streams of people who have me in their Circles. Is there any way to accomplish this?
when you make something public it defaults to displaying on the streams of people who have you in their circle. There's no way around this except for those people to not have you in their circle or to block you. Same idea as with Facebook public posts.
Why would people circle you if they didn't want to see your posts? If you are worried that you will be seen as spamming people, you can suggest that they put you in a circle whose volume is turned down or turned off completely.
Public posts are just that - public. You shouldn't need to worry about how people will find or follow them, that is something that each person who wants to follow you can control themselves.